The MP enjoyed the support and sympathy of many of his colleagues in the Congress party when he resigned from external affairs ministry in 2010. This time will be different.

Months after Shashi Tharoor resigned in 2010 as minister of state for external affairs following the IPL scandal, a key UPA minister admitted that as a colleague and foreign affairs expert he was "simply brilliant".

Tharoor enjoyed the support and sympathy of many of his colleagues in the Congress party then. That support helped him, apart from his own abilities, to return to Manmohan Singh's council of ministers in just two years, in 2012, as the minister of state for human resource development.

But now, as the mystery over the sudden death of his wife Sunanda Pushkar unfolds, the Thiruvananthapuram MP may find himself bereft of friends and any support from the party.

On Tuesday, Delhi Police announced that Pushkar was poisoned to death. "Delhi police have registered an FIR under Section 302 in the Sunanda Pushkar murder case. The medical report says she was poisoned," said police commissioner B S Bassi.

As the spotlight is again on Tharoor, he may be headed for a long, lonely battle for his political survival, feel many of his party colleagues.

The Congress party nominated him, overlooking the claims of many seniors, as the chairman of the Parliamentary Standing Committee in July where Congress vice President Rahul Gandhi also became a member.

"If you look back, many local leaders' claims were also denied when he became the (Congress) high command's choice for the Thiruvananthapuram seat," said a senior Congress leader.

But the party cannot be seen involved with Tharoor on his personal legal issues. It would like to see Tharoor clearing his name from the alleged murder mystery, said sources.

The standing committee chairmanship is likely to remain with him for the time being, as Tharoor does not face any direct charges. But if more fingers are pointed at Tharoor, the party may ask him to step down, said sources.